US 3005728 A
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Oct. 24, 1961 D. J. BRIDGEFORD 3,005,728
CELLULOSIC LAMINATES Filed Oct. 19, 1956 IN VEN TOR.
bag/a5 Jmdgefo mi BY m, QM, 3pm VWM United States Patent O 3,005,728 CELLULOSIC LAMINATES Douglas J. Bridgeford, Chicago, lll., assignor to Tee-Pak, Inc., Chicago, Ill., a corporation of Illinois Filed Oct. 19, 1956, Ser. No. 616,934 34 Ciaims. (Cl. 117-118) This invention relates to flexible laminates of cellulosic material having a thin coating of hydrophobic polymer bonded to one or both surfaces thereof, and means and methods of forming such laminates.
Although not limited thereto, the invention has Wide application to yfood packaging and particularly in the meat packaging industry where it has become desirable to provide substitute for animal casings used in stung sausage meats and the like. Casings formed of animal intestines and like materials have a tendency to stretch and change shape during the stuing operation, with the result that slices cut from the packaged meat have different and unpredictable diametric dimensions. In this age of pre-packaging, this non-uniformity of size adds serious complications to a desire to provide packages of sliced meat having a constant number of slices as well as weight per package. 'Ihere is also the ever present problem of resisting spoilage .of the packaged meat or other food product. v
As a substitute for animal casings, a number of different materials have -been developed, most of which are cellulosic, that is, include cellulose, regenerated cellulose, or a cellulose derivative in their composition. One such material is known as cellophane. Another is formed by pressing together cotton linters or other bast fiber product having a high porosity and degree of penetrability yfor viscose, to form a non-woven sheet which is then impregnated with regenerated cellulose. `Casings of such iibrous material are made by using a mandrel, and formin-g a tube thereabout from a web of the cellulosic fiber and then squirting a stream of viscose lbetween the overlapped plies of the web to form a seam while simultaneously extending viscose around the outside of the tube. The process is completed by passing the formed tube through a coagulating bath, then a regenerating bath and followed by washing and drying of the tube. Thus the tubing may be described as a cellulosic liber sheet to which has been applied a thin coating or skin or layer or application of viscose regenerated in situ. This material is known in the trade as brous strength, and by reason of its non-woven character, tends to retain its shape without stretching. However, like other cellulosic iilms, it has a relatively high oxygen and moisture vapor transmission;
Thus a principal object of the invention is to provide means and methods of treating cellulosic films, whether in sheet or tubing form, to provide a barrier to or at least reducev their oxygen and moisture vapor transmission characteristics.
Another object of the invention is to provide an oxygen and moisture vapor barrier coating for cellulosic lms.
Various hydrophobic materials are known which willA It has good ice utility in combating the problems of shrinkage of the packaged meats through moisture loss and should also delay spoilage because of the barrier it forms to oxygen the fact that the laminated product must retain an exceedingly pliable and flexible nature, under both dry and wet conditions, without separating to be useful as casing material into which sausage meat and the like may be stuifed.
It is therefore a principal object of the present invention to provide a flexible lamination in which a hydrophobie resin or polymer is strongly bonded to a cellulosic base and method of forming the same.
A further object of the invention is to provide a sausage casing embodying flexible fibrous sheet material coated with a thin layer of a hydrophobic polymer to provide a moisture vapor and oxygen barrier yfor the cellulosic material without materially affecting the other properties of the cellulosic material, such as its strength and flexibility.
Still another Objectis to provide means and'methods` of strongly bonding thin layers of hydrophobic polymer including the copolymer of vinylidene chloride and vinyl chloride, vinylacrylonitrile copolymer and other synthetic thermoplastic resins which do not contain active hydrogens, but are characterized in having great flexibility and resistance to alkalies, acids and solvents, including water.
The invention in its broader aspects is however not limited to the bonding of such active hydrogen free lpoly- -rners to cellulosic films and thus a further and broader object of the invention is to provide means and method of modifying the surface characteristics of hydrophilic organic materials which contain active hydrogens whereby thin layers or coatings of `various hydrophobic polymers, some of which do and others of which do not contain active hydrogens, will have improved adherence thereto.
Many other objects as well as advantages of the inl vention will be or will become apparent from the description thereof which follows, and it will be understood that many changes and/or modifications in the described process and resultant laminate may be made, and are intended to be included within the spirit of the invention as dened in the appended claims.
1Cellulosic materials, such as the cellophane and fibrous material referred to above, which are conventionally used in forming casings are essentially hydrophilic while the polymeric materials which I desire to bond to the cellulosic base are more nearly hydrophobic. The materials do not have a natural 4aiiinity one to fthe other, and attempts to laminate a thin iilm of the polymer to the cellulosic base or to coat the surface of the tlexible cellulosic sheeting with a solution of the polymer to produce thin layers thereof have generally not been satis- Ifactory, and the polymer layer readily separates, especi- Ially in the presence of hot water, as in cooking a food contained in the coated package.
However, in accordance with my invention, l have found that if I treat normally hydrophilic cellulosic sheet material, with a relatively dilute solution of an organic isocyanate, such as stearyl isocyanate or toluene diisoeyanate, I can cause a-reaction to take place on the surface of the cellulosic material to a superficial depth which is yet suicient to convertv lsaid surface from its normally Patented Oct. 24, 1961 3 hydrophilic character to one possessing hydrophobic characteristics (such surface modified llnis have beenV found to possess a one-to-five fold less rate of moisture vapor transmission than to the untreated films), and to which modcd surface, thin coatings of the hydrophobic polymer will strongly bond. An example of a lamination in accordance with my invention is illustrated'schematically by the figure of the drawing.
Although the proportions of the surface modifying jagent which I use may be varied somewhat, as forexample between l and .0055 by weight of the liquid vehicle, when I treat Waterwet regenerated cellulose films as they come from the softener bath, I prefer a 1%V solution of anvisocyanate, such as Itoluene diisocyanate. This I dissolve in isopropyl ether or in an equivalent organic solvent which has enough polarity to Wet the moist casing while having a very modest soluibility in water. Eirarr'iples of such other solvents include benzene, toluene, xylene, carbon te'rachloride, amylace'tates, higher ketones, proprietary aliphatic solvents and the like.
' `Instead of coating from organic solvents, it is also in keeping with the invention to coat from 'a latex or emulsion Vof ythe selected isocyanat'e. Thereafter, I coat the thus modified surface casing `with an organosol dispersion of the hydrophobic polymer.y For example, I may coat vinyl chloride-vinylidene chloride copolymer in methylethyl ketone or vinyl acrylonitrile in a similarly compatible organic solvent. After baking at moderate temperat'ure the polymer layer is found to have excellent adherence t'o the cellulosic base.
Teststo check the adherence of the polymer coating to such modficd cellulosic surfaces indicated that a 'maximum only 1 or 2% ofthe coating would be removed after a three hour tap water boil test.` The laminate remains flexible and transparent with little or no discloration. VStorage of the laminate at V 30 F. for a period of one week followed by vflexing and crumpling `does not give rise to cracks that can be seen through a low power microscope.
A One of the important characteristics and advantages of films fcoated according to the present invention is that very little, if any, free isocynate groups are left in the surface after t-he baking. It is therefore possible for the films to be treated with the isocyanate and then stored for several months before coating. Adherence is apparently obtained through chemisorption forces and thus distinguishes over prior art processes wherein relatively thick layers of polyisocyanates have been used as an adhesive to chemically bond twofilms together.V
For best adherence, the "hydropho'bicity of the r'esulfting underc'oated cellulosic, film is controlled in accord'- ance with the hydrophobic `character Aof the' selected polymer coating. Through the proper choice of reagent or concentration of the reagent in the solvent, and the extent to which theundercoating reaction is allowed to penetrate into the Vcellulosic filmV a 'moded surface 'may be produced having Vau immediate water contact angle varying all the Way from 30 to 140, For example meta-nitrophenyl isocyanate when used to undercoat cellulose will give an undercoated l'rn with a moderate degree of water repulsion as indicated by an immediate contact angle with water of 50- 70 degrees. Diisocyanatodiphenylmethane, lon the other hand, 'even when used from a solvent in trace quantities, gives rise to a waxlike surface with a water vcontact angle of over 90 degrees.
Although the invention is not limited to superficial modification of the cellulosic film, this is highly 'desirable from a point of economy of materials, and also to avoid deleteriously changing the essential properties of the undercoated film. Under ordinary circumstances it is possible to obtain effective bonding where the modification Confining of the undercoating or reaction process to the surface area of the cellulosic film 'can be accomplished in any one of several ways;
(a) The isocyanate may be applied to the cellulosic film by methods that ensure a very thin film of the isocyanate. These methods include application by offset from a roll, doctor rods or blades applied with thin spacing, printing, use of fine aerosols of the pure compound or solutions, dusting, and numerous other methods known to the art.
(b) The isocyanate may Ibe applied mixed with Yrelative volatile solvent whereby the solvent evaporates before the isocyanate has had time to diffuse vto any extent into the cellulosic body.
(c) The isocyanate may be applied to thecellulose film with a solvent that has a low miscibility with water or other liquid contained in the body of the cellulosic film. Such solvents include benzene, toluene, carbon tetrachloride, higher keto'nes, ethcrs, ester, and the like. For example, 'when using tolylene 2,4-diisocyanate for undercoating, a given water drop contact angle on the cellulose film (say degrees) can vbe obtained from a solution of 0.25% in toluene Vand 1.0% inV diisopropyl ether. Generally, as the Water miscibility of the solvent decreases, the undercoating reactions are restricted to avery thin outer layer of the cellulosic film.
(d) The isocyanate that is used as the reactant maybe selected Vto have a low solubility in the liquid 'within the cellulosic film or to have a molecule size so large that it cannot easily diffuse into the gel phase of the cellulosic material. Examples of isocyanate so characterized includes diisocyanathodiphenylrncthane and triiocyanatotriphenylmethane. Also, some of the polyurethanes with i'socyanate functions at both ends of the molecule are too largeto diffuse appreciably into the cellulosic film, particularly when it is air dry.
The undercoa'ting or surface modifying process is considered to involve the formation of cellulose urethaue's on the 'surface of the film, as well as 'the formation of several by-products in various ratios dependent on ltheir relative reactivity. Thus, in treating cellulose containing water with a ieac'live monoisocyanate, undoubtedly the main byproducts are ureas of low molecular Weight while when treating the same film with a di-isocyanate, both monomeric and polymeric ureas of various molecular weights are formed. When both water and glycerol, or water and othe active hydrogen containing materials are present, deposition of both polymeric ureas and polymeric urethanes will occur in the surface of the cellulosic film. Although the hydrophobicity that normally arises on the surface of the cellulose film is due in part to the formation of cellulose urethanes and in part to the deposition of these byproducts, best Vadhesion Vseems to require the formation of the compound with cellulose. This is borne out by the fact that good adhesion of the polymer coating can be obtained with dry glycerol-free cellulose films which have been undercoated 4with a monoisocyanate, for eiiample.
In treating moist casings, concentrations of up to 1-.l1 percent ofthe isocyanate are to be preferred because of the .possibility of losses through dissolution and/ or reaction with the larger amounts of Water present in the film. However, when treating dry casings with isocyanates dissolved in such water immiscible solvents as toluene and carbon tetrachloride, sufficient hydrophobic cellulose surfacescan be obtained with reagent concentrations a's low as 0.05 percent. Dry casings will ordinarily contain 20 to 25 glycerol and 5 to 8% Water` Thus the incidence of side reactions in addition to the cellulose urethane formation will be less than when the wet gel nlm which contains at least 50% Water is used. 4Preferably the concentration of isocyanate should be sufficient to produce a thickness of the isocyanate-reacted cellulose on the cellulosic film or sheet which roughly approximates 0.008 mil- Although the examples, thus far, have been limited to the use of toluene diisocyanate and stearyl isocyanate, a relatively Wide range of mono, dior tri-isocyanates and related isothiocyanates can be reacted with the cellulosic surfaces to provide adhesion yfor the coating to be subsequently applied. 'I'hus for example, diisocyanatodiphenylmethane may be used. This has a higher ratio of aromatic hydrocarbon to polar isocyanate groups than has toluene diisocyanate and its reaction with cellulose provides greater hydrophobicity. Moreover, its lower Water solubility permits a greater restriction ofthe reaction to the surface of the cellulosic film or casing which is desirable both from an economy of material as well as the low toxicity level it permits in the final product. Preferably, such a material is used in a solution of 150 parts per million to 600 parts per million in a toluene-isoamyl acetate solvent mixture. Fibrous casing thus treated when coated with 0.4 to 0.6 mil coatings of saran resin showed good adhesion to the casings after a three-hour tap water boil.
Alpha-naphthyl isocyanate is also useful when suitably diluted in a relatively water-immiscible organic vehicle as aforedescribed to convert or modify the surface of a cellulosicv ilm and obtain strong adherence of a hydrophobic polymer coating thereto. In utilizing this particular isocyanate to bond a coating of a copolymer of vinyl chloride and acrylonitrile existing in an 80:20 ratio such as sold under trademark Vinyon 1N, it has been found preferable to use a 0.1% solution "while it is preferable to use an 0.6% solution when it is desired to bond saran to a brous sheet.
Although the invention has thus far been largely contined to a discussion of the modification of the surface of regenerated cellulose or brous material, it should be understood that the invention is applicable to that class of active hydrogen containing hydrophilic materials which include, in addition to the afore mentioned cellulosic materials, cellulose and substituted cellulose derivatives, paper, cotton, wool, silk, zein, polyvinyl butyral, amylose and the like.
Likewise, although the invention has particular importance in improving adherence of polymer coatings not containing active hydrogens to hydrophilic lms, the invention is not so limited, and a large variety of materials including those that do and those that do not contain active hydrogens may be caused to have improved adherence to cellulosic films or to other hydrophilic hydrogen containing material followng the teachings of the present invention. Examples of coating materials in addition to those previously mentioned include chlorinated rubber, polyethylene, wax and/ or polyethylene-modified cellulose nitrate, cellulose acetate, or ethyl cellulose. Also rubber hydrochloride and vinyl copolymers, such as vinyl chloride-acetate resins which are available commercially in various proportions.
In general, reactants With which the surface of such cellulosic materials are treated will include organic compounds such as the aforementioned mono-di-, and polyisocyanates, which contain a plurality of -X=C=Y groups wherein X is -C or N and Y is O, S or NR wherein R is hydrogen or mono-valent hydrocarbon radicals. The preferred classes are aromatic isocyanates, such as toluene 2,4diisocyanate and 2,6-diisocyanate; alkyl aryl isocyanates such as diisocyanatodiphenylmethane or triisocyanatotriphenylmethane; aliphatic isocyanates, such as stearyl isocyanate; aromatic isocyanates, such as alphanaphthyl isocyanate, or phenyl isothiocyanate; substituted aromatic isocyanates, such as meta-nitrophenyl isocyanate; aromatic-aliphated isocyanate substituted urethane such as the reaction product of two moles of toluene diisocyanate with one of ethylene glycol or of two moles of toluene diisocyanate with one of hexamethylene glycol; isocyanate substituted ureas such as the reaction product of two moles of toluene diisocyanate with one of ethylenediamine; isocyanate substituted aromatic ureas such as the reaction products of two moles of toluene diisocyanate with one of p-phenylenediamine; or trisubstituted urethanes such as glycerol reacted with three moles of toluene di-isocyanate. Also useful are 2-biphenyl isocyanate, 4-biphenyl isocyanate, n-butyl isothiocyanate, 2,5-dichlorophenyl isocynaate-o-ethoxyphenyl isocyanate, p-ethoxy phenyl isocyanate, 2-methoxyphenyl isocyanate, o-nitrophenyl isocyanate, p-bromophenyl isocyanate, oand m-chlorophenyl isocyanate, ethyl isocyanate, ethyl isothiocyanate, m- .nitrophenyl isothiocyanate, phenylisothiocyanate, phenyl isocyanate, beta-naphthylisocyanate, o, m, and p-, tolyl isocyanate. Mixtures of the aforementioned may also be used.
In addition, other isocyanates and isothiocyanates, including vinylarylisocyanates of U.S. Patent No. 2,468,- 716, the propenyl isocyanates of U.S. Patent No. 2,325,- 287, the alkyloxyphenyl isocyanate polymers or copolymers of U.S. Patent No. 2,647,884, the alkyl isocyanatesethyl acrylate copolymer of U.S. Patent No. 2,537,064, the alkyd-unsaturated isocyanates described in U.S. Patent No. 2,503,209, reaction products of bis phenol and isocyanates of U.S. Patent No. 2,594,979, diisocyanate modified poiyesters containing an excess of isocyanate groups, polyisocyanate-modied active hydrogen containing rubber, also ethylene diisocyanate, tetramethylene, diisocyanate, hexamethylene diisocyanate, decamethylene diisocyanate, 2,3-dimethyl-tetramethylene diisocyanate or diisothiocyanate and propylene-l,2, butylene-l,2 and bu- Y tylene-l,3 derivatives of diisocyanate and diisothiocyanate, toluene diisocyanate, diphenylmethane diisocyanate and triplienyltriisocyanate. Other exemplifying aromatic polyisocyanates and isothiocyanates include m-phenylene, p-phenylene, Xylyenel,4 and 1,3; l-methylphenylene-2,4; naphthlene 1,4; benzene 1,2,4 triisothioyanate; 5 nitro- 1,3 phenylene diisocyanate; 4,4'diphenylenepropane diisocyanate, and lanisole polyisocyanate. y
Operative alkylidene derivatives include ethylidene diisocyanate, heptylidene diisocyanate and heptylidene isothiocyanate, for example. Aliphatic-aromatic compounds include phenylethylene diisocyanate, styrene diisocyanate, allyloxyphenyl isocyanate and the like. Cycloalkylene derivatives include cyclopentylene diisocyanate, 1,4-diisocyanatocyclohexane, cyclohexylene-1,2-diisothiocyanate and the like.
Polyisocyanates and isothiocyanates which include hetero atoms, for example, l,2,3,4-tetraisocyanatobutane, Z-chloro-1,3-diisocyanatropnopane,
SCN (CH2 3S (CH2) aNCS,
and the like.
The following more specic examples are illustrative of the process:
Example vI An approximately one percent emulsion of octadecyl isocyanate in Water was made by adding tive milliliters of the isocyanate to about 480 milliliters of water, rapidly stirring in a Waring Blendor Iand then adding approximately l0.2 gram of Atlas Tween 60 emulsiier. This emulsilier is polyoxyethylene sorbitan monostearate. The emulsion was stable against creaming for at least three days.
This emulsion was used to dip-coat a casing of ibrous material with a contact time of 0.2 to 0.4 second. The moist casing was then dried for five minutes at C. The casing still had a hydrophilic surface after the treatment but it was coated with saran. The treated film was dip-coated in an eight percent solution of 200-centipoise resin in 3:1 tetrahydrofuran: acetone mixture. This coated casing was air dried over the weekend and then dried at C. for thirty minutes. The somewhat wrinkled casing was cut into-about tive-inch cylinders, slit and boiled in tap water for three hours. The six pieces were blotted and one-inch wide Texcel pressure sensitive tape was applied and immediately ripped otf. The estimated average-of tests on both directions of the casing was about 30 percent removal. l
7 Example Il An additional batch of 300 milliliters of emulsion was made by weighing out three grams of lthe octadecyl isocyanat'e and adding to it 0.1 of the Tween 60 with mixing. This "mixture wasthen slowly added to most of the water and rapidly lstirred in a Waring Blender. The beak'er was washed 'out with the remainder of the water. An apparently stable emulsion was formed. A fibrous casing was pretreated with this emulsion and then coated with sai-an a's in Example I. Similar adherence results were obtained. The isocyanate-treated casing was nuclh more hydrophobic than that produced in Exampe By adherence as opposed to adhesion is meant the measure of the attraction between the two surfaces under the particular method of testing where the elongation Vof the coating, the rate off application of force and the nonplanarnature of 'the surface to which the coating is applied all obscure the inherent attraction between the coating and substrate. Adhesiom on the other hand, is the attraction between two surfaces when the separating force is applied normal to them. It is applied fast enough so that little elongation of the coating occurs and the interface of the coating and substrate is essentially plane.
.Exemple III Toluene diisocyanate was made a's a 1.11 percent solu-A tion in practical grade diisopropyl ether. Dry fibrous casing was dip-treated in this solution for 0.5 second. Heating the treated filmv at 120 C. for three minutes resulted in a hydrophobic surface which required about ten minutes for a drop of water to penetrate. The treated film was-dip-coated in ah 8 percent solution of ZOO-centipoise s'aran resin inV 3:1 tetrohydrofuran acetone mixture.Y
A coating tower was utilized which allowed four legs of casing to pass through it with the aid of idler rolls and one drive roll at the exit end. The length of the casing in the cabinet is about 40 feet. The rtemperature of the heating banks at the first leg of lthe casing travel was controlled to about F. The casing passes up-leg from the coating tank 'and Wiper rods -for about nine feet before it encounters the first roller. An improvised flash Y bake apparatus was inserted below the cabinet between the second and third legs of the casing. This consisted of two hot plates facing each other with the casing passing up between them so that it did not come in contact with a roller for about ten feet olf travel. VThe temperature o`f the hot plates was variable.
Untrea'ted A)fibrous casing was iirst used for the coating trials to .find the conditions required to obtain an `essentially solvent-free Saran Fibrous casing was passed through an 8% solution of Saran .resin in methyl ethyl ketone and .given a light wipe. The solution had a viscosityof 'll-3.2 seconds in a General Electric No. 2 Zahn cup. Casing was passed through the cabinet at 3.88 feet per minute with the heater banks 'set at 24S-255 F. The dash bake set-up was-arranged so that the middle of the air gap was at 145 C. and the actual temperature of the casing passing through was about 1Z0-125 C. Solvent odor was noted at theash bake so that some must have been removed at this point. After preliminary diihculty in tracking and-other adjustments in the cabinet a uniform casing was obtained.
Adherence of the approximately 0.1 mil Saran coating was-tested by boiling five-inch, slit-open cylinders of the casing in tap water and testing with Scotch tape as `previously described. While no sloughing was noted the coating was completely removed by the tape.
Example V The conditions of Example IV were maintained except that the librous casing was passed through the coating cabinet at 9.46 feet per minute. This casing was given the tap water boil and adherence tests. The coating became cloudy shortly after immersion in the boiling water and sloughed olf in about ten minutes.
Example VI A 1.11 percent solution of toluene diisocyanate in diisop'ropyl ether was prepared. This solution was placed in a live-inch by six-inch area stainless steel tank six inches tall which had a wooden roller one inch from the bottom. Well-wiped iibrous casing was passed ldirectly from the glycerol softener tank into the experimental tank with an immersion timeof two seconds. A wiper rod set-up wasV situated about ten inches from the surface 'of the liquid of the tank. The casing Was passed into the slack boxes and then through the dryer. The casing was heated at an air temperature of 205 F. for six and a half minutes. The resulting lm was 'somewhat hydrophobic in that a drop of water placed on it at the dry end of the dryer spread about 40 percent less than on the control and required about ten minutes to -Wet through. About 280 feet of this surface-modified lm was made together with 200 feet of unmodified control llm. It was noted that lthe solution of the diisocyanate left from the test became cloudy in about three hours from the start of the test. A substantial amount of precipitate settled in about one day.
Fibrous casing which had been treated with the toluene diisocyauate solution was given an approximately threeinch dip in an eight percent solution of Saran in methyl ethyl ketone and `given a light wipe. lt wa's then passed at 9.46 feet per minute through the cabinet which 'was held at 290 F. The surface temperature ofthe casing at the dash bake was about 255 F. The `casing was immediate-ly tested for coating adhesion as usual. The coating resulting from the cabinet was uniform in appearance while that from the three-hour tap water boil was slightly cloudy on one side of the liat casing. The twosidedness was caused by running the casing closer -to one heater bank than the other. Residual solvent lin the polymer coating that was not completely dried decreased its adhesion to the undercoated cellulosic film.
it was noted that the coating was removed completely from the side which had a cloudy appearance but not more than one to two percent-of the coating area under the Scotch tape was removed from the other side. In each of the present experiments the coating towerwas operated for from fifteen to twenty minutes so that reasonable assurance was present that equilibrium obtained; This was done because of `the large temperature gradient in the cabinet which required time for establishment.
Example VIII made somewhat hydrophobic by reacting them as a wet gel film with a dilute solution of toluene diisocyanate in diisopropyl ether while in the following examples a dry glycerol-containing iilm was reacted with the isocyanate undercoating reagent. In these latter examples, the coating tower as described in Example IV was utilized and the fibrous casings were made hydrophobic by uudercoating them with a one percent solution of 2,4-toluene diisocyanate in either n-amyl acetate or diisopropyl ether. Undercoating was accomplished at ten feet per minute. The Saran resin was coated on -brous casings at rates as high as thirteen feet per minute and cabinet heaters banked at 340 F.
Weight-loss storage tests made on liver sausage stuffed in casings coated with about 0.12 mil Saran resin indicated losses of from 2.30 percent to 6.70 percent for a seven-day storage, whereas uncoated liver sausage lost about 16.5 percent in weight. It was further noted that the Saran coated liver sausage remained pink in color.
Example IX A fibrous casing in air dry state was made somewhat hydrophobic by passing it for six seconds into a rone percent solution of toluene 2,4-diisocyanate -in n-amyl acetate. 'I'he casing was then passed through the coating tower at 9.46 feet per minute to give a reaction time of about four minutes. About 40() feet was uudercoated with heater banks of the coating tower set at 150 F. About 100 additional feet of casing was lproduced with the tower held at 205 F.
Example X 'Ihe solvent for the 2,4-toluene diisocyanate was changed to diisopropyl ether. A one percent solution of the isocyanate was made up in the more water-soluble and lower-boiling solvent. Using this solution, about 1000 feet of iibrous casing was uudercoated at 9.46 feet per minute and 150 F. About 150 feet of casing was also uudercoated at 205 F.
Example XI The concentration of toluene diisocyanate in the diisopropyl ether was increased to two percent and about 500 feet of casing was uudercoated at 150 F. It was noted that both solvents wet the dry casing. Furthermore, the diisopropyl ether seemed to penetrate the casing as evidenced -by liquid inside. The n-amyl acetate did not penetrate. After the casing was running in the diisopropyl ether for a few hundred feet the penetration was not so evident. All treatment conditions used made the cellulose hydrophobic in that a drop of Water placed on it did not immediately spread and it required about iive minutes to wet the casing or soak partly in. The immediate contact angle of water on the casing was about 60.
Example XII As a control, casing from the same reel as was undercoated above was coated with Saran resin but without the hydrophobic undercoatng. The casing was coated for about a 20-minute period at speeds of 3.88 and 9.46 feet per minute with the heater banks in the cabinet set at 250 =F. The actual surface temperature of the casing passing through the liash bake was 120 to 125 C. It was noted that the casing was tacky at the ash bake. In both cases the coating did not Slough ot in the adhesion test but it was easily removed by rubbing.
Example XIII The same eight percent solution of Saran resin in methyl ethyl ketone which had been used to coat the control casing was used to coat casing which had been made hydrophobic by reaction with two percent solution of toluene diisocyanate dissolved in diisopropyl ether. About 200 feet of uudercoated casing was coated from the 24centipoise Saran solution without wipe rods.
*The conditions of Example XIII were followed except that the flash bake was set so that the casing surface was at to 150 C. The flash bake in the case of both Examples XI and XII was yfor three seconds. The casing was slightly browned but appeared to be uniformly coated. Scotch tape removed one to two percent of the coating after the three-hour water boil.
Example XV The conditions of Example XIV were followed except that t-he speed of passage of uudercoated casing through the cabinet was increased to 13 feet per minute. Some offset on the idler rollers at the top of the heater banks was noted and some scratches were noted on one edge of the casing. Itl was concluded that the temperature was too low for this rate of speed.
The temperature was increased to 325 P. and more coated casing was produced. About 13 minutes of casing production was coated. This casing had been undercoated with two percent toluene diisocyanate solution. Fibrous casing which had been uudercoated with a one percent toluene diisocyanate solution now passed through the cabinet and was coated. The coating did not appear scratched although an occasional small blister was noted about an inch from the edge of the casing. No more than five percent of the area of either of the iilms could be removed with Scotch tape after a three-hour water boil.
The casings produced in these examples were stuied with liver sausage, and it was observed that, although a 0.12 mil Saran resin coated casing stuffed with liver sausage lost an average rof 0.57 percent of weight per 24 hours which was too great a weight loss, this could be remedied by approximately doubling the thickness of the Saran polymer layer. It was, however, noted that even a 0.12 mil iilm of Saran resin afforded enough protection from oxygen that the liver sausage remained pink at least one week Iwhile the control became brown through the outer quarter inch of circumference and grey on the inside. The above Weightloss was carried out at temperature of 54 to 58 F. showing a 0.4 percent per day loss using Saran coated casings as against 2.23 percent per day weight loss for uncoated casings.
Example X VI A titanium dioxide loaded casing uudercoated with toluene diisocyanate was used for coating with 1000 centipoise Saran resin solution. The casing Vwas dipped into a l5 percent solution of Saran in methyl ethyl ketone, given a medium wipe with coarse doctor rods and passed at 6.17 feet per minute into thetower. The coating dope had a Zahn No. 3 cup viscosity of 28.2 seconds or about 250 centipoises. The coating tower heater banks were at`300 F. with the second leg travel at 220 F. The casing in the six seconds flash bake between the second and third leg was held at C.
It was noted during the irst l5 minutes of production that bubbles formed in the coating, especially along the edges. Reducing the temperature to 290 F. did not reduce the number of bubbles so the Saran concentration inthe dope was reduced to about 14 percent and viscosity was reduced to about 200 centipoises. While blisters were not completely eliminated by these changes, they were greatly minimized.
A total of 50 minutes of production was reeled and a sample of coated casing under the latter conditions was taken for cutting into .20-inch pieces for stuffing.
1 1 5' 'Portions of the Saran `coated .casing were boiled in tap Water for 'three ihours. 'there was no sloughing. The coat-ing could not be rubbed ott but .Scotch tape removed it completely. The Saran coating was removed in small shreds with diiiculty Aby scratching. The casingfremoved With Scotch tape was :slightly `turbid and showed .some particles of Titanox embedded in the resin film. Part of the coating of the casing had crooked :alud this superiicial pigment .contributed toV relatively poor coating adhesion. Thickness measurements were Amade on coating removed from the .casing by embrittlement o'f the casingwith concentrated hydrochloric acid over night. The thickness was measured with the Carson Electronic Micrometer on those .areas of the llm which did not reproduce a washboard or rippled surlface'from the casing. Additional measurements Were made on a coating stripped from Saran-coated librous which had not been undercoated. Thickness .ranged from 0.25 V.to 0.32 ymil with Van average of V0.3 mil.
Five liver sausages stuled .into the casings averaging 0.72.5 to `0.23 mils in thickness .of .Sar-an resin coating .were discovered to have lost an average of 0.* ,percent per day in weight overa l7-day storage period. At the end of the storage period all sausages. were pink over 99.5% ofthe areas. A tfew browned areas were .noted as also a few green -molds .on the ends of Athe sausages. The odor was still good.
While thecoating Acould be removed with Scotch 'tape after .a three-hour tap water boil ithis may not represent a smaller adhesion than that obtained with lthe 0.14 mil Saran coating. .The thicker coating may permit greater grab .from the .plast-icizer .of the adhesive-onthe test Scotch tape. However, .the .adhesion of the. .thicker *Saran .coating Ais adequate lfor stung and cooking. Liver sausage stuffed .in 0.3 mil Saran coated casings llost only 0.1`5 Apercent of Weight per day when stored vat l5 F. and remained pink yessentially free .from .mold'for at least 17 days at said temperature.
.Example X VH This is an example .of the use of p,p'diisocy'a'natodi phenylmethane (DDM) as the 'surface modifying reagent. About 2.4 grams o'fp,pdiisocyanatodiphenylrn'ethane was ground in a mortar and sifted into 300 milliliters oit Yisoamyl acetate which was held at 70 C; About `1 00 milliliters of toluene was added and the mixture was stirred five minutes. About 'half the solid dissolved. When 'the `solution wias cooled `to 4room 'temperature most of the vsol-id precipitated. The supernatent liquid'was decanted "and used foi reaction with cellulose surfaces. Later large scale solubility tts showed `th'at'tlze 3: lri'soamyl'acetate-toluene solution dissolved 600 'to '620 `parts per "million of active material.
The dilute solution was .placed in an '.evaporat-ing dish and four foot lengths ofjbrons .casing were dipped through it with -a contact time of 0.2 to 0.4 second. The casings wet with the solution were :placedffor a few minutes lin front of the hood, then they Were'hea'ted three minutes at 135 1C. The casings obtained a waxlike surface which water showed no signs of wetting in ve minutes. Water drops began to soak through :after 25 minutes.
.'I-he saturated solution of diisocyanatodiphenylmethane was diluted 'l :'l (v./v.) with'isoamyl acetate and additional pieces of casing were treated. A300 parts per million solution also gave hydropholicity.
.A lSOVpartsper million and a 75partsper'mil1ion solution were .also prepared vby diluting the saturated `solution in '3:1 isoamyl acetate toluene withiiso amyl acetate. When these were used 'to react with the cellulose casing as 'before .the 150 parts'pe'r million solution gave a hydrophobic surface while that .obtained with the '75 parts per million DDM solution was much less so. Pour lengths Yof `vcasing tour feet long were treated with each of vthe above solutions.
DDMreacted casing 4was coated with V100G-centipoise saran from an eight percent solution in methyl ethyl ketone. The coated casings were air dried over night and dried at 135 C. for 25 minutes the next morning. The adhesion of the saran to the modified casings and to the non-undercoated controls was estimated vby boiling coated pieces in'tap water for three hours and attempting removal of the coating with .Scotch tape. About 20 tests with l x 4 inch tape were performed on each type of coating.
A solution of 500 parts per million of DDM was made in n-amyl acetate. Other casings were dipped into this solution, the solvent was'evaporated and the casings were heated at 135 C. for three minutes. All casings vbecame hydrophobic. It was noted that the casings were not hydrophobic on their interiors. It was further noted that y they could ybe extracted with water and dried several times and the surface remained hydrophobic.
Adhesion tests were conducted as in Example XV II:
Average Sample Coatln g Range,
Removed Percent Percent A. Y l. 5 0-5 B 17. 0 3. 35 C 0 Fortheadhesion tests the casings were coated with Saran as in the prior example, but they were 'force-dried .for 25 minutes at C. The same day they were coated.
Example XIX This is an example Vof the 'use of alpha-naphthyl isocyanate as ithe surface modifying reagent. One milliliter of alpha-naphthyl isocyanate 'was dissolved in 200 grams of methyl isobutyl ketone. The solution was poured yinto an evaporating Vdish and .several threefoot lengths of lbrous casing were dipped through and .allowed to drain. They rwere air .dried :at room temperature :and .divided into two groups. One :group was' heated at 135 1C. :for three minutes while the other was heated for 'fou-r minutes. The surfaces ofboth groups of casing became hydrophobic with an instantaneous contact angle of about 70 .with water drops. A drop of Water of 0.05 milliliter spread over Ian area about 0.6 centimeter square. While the casing did not immediately pucker up or crawl around the drop a thin line on the .casing could be seenwhen the drop was blotted olf immediately after placement. The drop yrequired about veminutes towet andstart to soak into thecasing.
A i'0.1 percent .solution of lalpha-naphthyl isocyanate was similarly'prepared `and used to undercoat the-casing with afheating time of four minutes.
Inv .this instance a somewhat less hydrophobic coating was obtained .in that a waterdroplof 0;05 milliliterspread over an :area Jof about one centimeter square and began to wet the casingin about 40 seconds. 'It `showed animmediate contact angle of `about 30'.
Example XX 13 only ve percent of the area of the coating was removed. Rub and scratch resistance were excellent.
Example XXI This is an example of the use of vinyl chlorideacrylonitrile copolymer as the hydrophobic polymer coating. Vinyon N, a product of the Bakelite Division of Union Carbide and Carbon Corporation was obtained. One hundred grams of the powder were dissolved in acetone to make a 7.6 percent solution. 'I'he material dissolved slowly to make a dark amber viscous solution. A General Electric Zahn No. 2 cup indicated a. viscosity of about 180 centipoises. Wiper rods had to be used with a coating solution of this viscosity to obtain 0.2 to 0.3 mil coatings,
Three samples of casing were undercoated with 1.18 percent, 0.59 percent and 0.1 percent solutions of alphanaphthyl isocyanate in methyl isobutyl ketone. A heating time of three minutes at 135 C. was used. The undercoated casing was coated with the Vinyon N resin by dipping and wiping. It was dried at 130 to 135 C. for 25 minutes and coating adhesion was tested immediately.
Casing Coating Adhesion 1. 1.18% undercoated Vinyon N Average 75 percent coating was recoated.
moved. Excellent rub and scratch resistance.
Average 25 percent coating was removed. Range -60 percent. Excellent scratch and rub resistance.
Average 40 percent coating was removed. Good scratch and rub resistance.
Five percent of coating was removed. Excellent scratch and rub resistance.
2. 0.59% undercoated Vinyon N coated.
3, 0.1% undercoated Vinyon N coated.
4. 0.1% undercoated Vinyon N coated. Coating heated 35 minutes instead of the usual 25 minutes at 130 C.
Example XXII Example XXIII This is an example of bonding a chlorinated rubber such as Parlon to fibrous casing made hydrophobic by undercoating with reaction products of diisocyanate diphenylmethane. This was done by immersing the casing for one second in a 600 part per million solution of diisocyanatodiphenylmethane in a mixed solvent, air drying for five minutes and passing continuously into an oven held at 135 C. The casing was exposed for two and a half minutes to this temperature. The mixed solvent used for the reagent was a 3:1 mixture of isoamyl acetate and toluene.
Pieces of treated and untreated casing were coated with 0.3 to 0.4 mil coatings of unplasticized l25-centipoise grade Parlon. The casings were coated by dipping into a ten percent solution of the Parlon in methyl ethyl ketone. Three-foot lengths of coated casing were allowed to drain vertically for fifteen minutes, and then were force dried at 130 C. for one and a half minutes. Both types of coated casing were placed in tap water at 70 C. after they had been cut into tive-inch cylinders and slit. The coating s-loughed o the untreated casing in less than one minute. The coating on the undercoated casing had not sloughed ott after two hours in tap water at 70 C. and only small shreds of the coating could be 14 rubbed olf. In the dry state the coating was percent removed from the untreated lm and about 30 percent from the undercoated film using Scotch tape. After hot water immersion for two hours the coating could be completely removed from the undercoated casing with Scotch tape.
The Parlon ilm has an elongation of about 3.5 percent. Consequently, when the wet cellulose casing was stretched the lm crazed, and could be easily rubbed off. Islands of coating appeared to ladhere to the casing.
In an elfort to observe the elect of a plasticizer on the coating adhesion and to increase coating elongation, a Parlon llm containing 20% dibutylphthalate plasticizer was coated on both untreated and diisocyanatodiphenyl-methane undercoated cellulose lms. The Parlon coating on the untreated casing sloughed off in two minutes when the film was placed in Water at 20 C. and in less than one minute in water at 70 C.
On the other hand, the Parlon coating on the diisocyanatodiphenyl undercoated casing did not slough off when placed in cold water at 15 C. vfor one hour, hot water at 70 C. for two hours, or boiling water for one hour. The coating blushed in the boiling water. In the plasticized state the coated casing could be stretched 10 to 14% before a turbidity appeared in the casing and evidence for islanding or checking arose. The plasticized Parlon casings could be removed completely with Scotch tape in dry or wet states.
Coating thicknesses on the undercoated casings were estimated by thickness measurements on free lms sloughed `from the control casing coated under similar conditions to the undercoated casings. Carson micrometer measurements on these free tilms averaged 0.34 mil with a range of 0.3 mil to 0.4 mil.
Cellulose nitrate, cellulose acetate and ethyl cellulose as film formers are major components of protective, decorative or barrier coatings. They are used along with waxes, dyes, resins, plasticizers and pigments in important coating outlets. Attempts were therefore made to bond such materials to cellulosic films. It was found that p,p diisocyanatodiphenylmethane underco-atings markedly improve adhesion of both plasticized and unplasticized cellulose nitrate and ethyl Vcellulose to cellulose casings. Stearyl isocyanate undercoating improved adhesion only slightly. Toluene diisocyanate and diisocyanatodiphenylmethane undercoatings had only slight eiect on the adhesion of cellulose acetate to brous casings.
Example XXIV Hercules Type AS nitrocellulose, viscosity tive second, was received wet containing 30 percent ethanol. This material was dissolved in acetone to make a four percent solution. Enough di-n-butyl-phthalate was added so that a lm containing 17 percent plasticizer would be deposited.
When untreated and diisocyanatodiphenylmethaneundercoated fibrous casings were coated by dipping into this solution, the coatings blushed as they dried. The coated casings were allowed to air-dry for two hours. They were then tested for coating adhesion by immersion in both cold water and boiling tap water. Plasticized nitrocellulose coating on the untreated casing sloughed o in cold water in ve minutes. The coating on the diisocyanatodphenylmethane-undercoated casing resisted two hours in boiling tap water. Scotch tape removed about ten percent of the coating after the boil. Scratch resistance was good.
Example XXV To eliminate blushing in these coatings a retarder was added to the acetone solution. This higher boiling solvent was methyl isobutyl ketone. The coating dope became about three percent nitrocellulose in a solvent 1:24:75 ethanolzmethyl isobutyl ketone:acetone.
Untreated casings and diisocyanatodiphenylmethaneaoosfrasv Vwater and in hot (95 C.) tap water. The nitrocellulose coating sloughed from the control or untreated casing in three minutes in cold water and in one minute in hot water. On the other hand, the diisocyanatodiphenylmethane-undercoated nitrocellulose did not` Slough olf in cold water after 24 hours and in -hot water (95 C.) after four hours. It showed good scratch resistance and a Scotch tape removal averaging ten percent after the hot water test.
Example XX Vl An v11.6 percent solution of Hercules Type AS nitrocellulose, viscosity ve seconds, in a solvent consisting of 94.4 percent ethyl acetate and 5.6 percent .ethanol was prepared. No plasticizer was added.
Untreated ibrous casing and one undercoated with diisocyanatodiphenyhnethane were coated b'y dipping and were permitted to air-'dry over night.
The two coated casings were placed in hot (95 C.) tap water as slit five-inch cylinders.Y The unplasticized coating on 4the control casing sloughed off in one minute. The coating on the diisoeyanatodiphenylmethane-undercoated casing had not Sloughed' olf after three hours of boiling in tap water. 'The coating began to lift around the corners after four hours at boil. The coating did not blush on either control or diisocyanatodiphenylmethane-undercoated casing. Scratch resistance was good and the diisocyanatodiphenylmethane-undercoated casing could be stretched eight percent without delamination.
Example XXVII Hercules ethyl cellulose Type N422 was obtained which has an ethoxy content of 47.7 percent and a viscosity of centipoises. It was dissolved in methyl ethyl ketone to make a five percent solution and enough di-n-butylphthalate was added Vso that the deposited ethyl cellulose film would be 30 percent plasticizer. Y
Both control and diisocyanatodiphenylmethane-undercoated fibrous casings were coated by .dipping with this dope and the coating allowed to air-dry over night.
The two types of coated film were placed in boiling Water. The coated control coating immediately sloughed oi. Y The coating on the diisocyanatodiphenylmethaneundercoated casing began to blush in about ten minutes. After two hours in boiling tap water the coating had not sloughed olf, and it could not easily be removed by scratching. It could -be more easily removed after the casing was stretched 3() percent. The lm was slightly tacky at boiling water temperature. Scotch tape removal of coating after the water boil averaged percent with a range of l0 to 60 percent.
Example XXVIII VThis is an example of coating fibrous casing with wax nitrocellulose layers. A fortified wax was made by melting 5.6 grams of Eastman Epolene .N with 112 grams yof paraffin wax, melting point 5456 E. The Epolene N is a polyethylene wax in the 200G-4000 molecular weight range and has an acid number of 9-l0. .Addition of it to parain raised the melting point to about 65 C.
A coating dope Was prepared as follows:
. Gm. Hercules AS-S nitrocellulose 25 Dibutyl phthalate V11,7 Modied iparatiin wax 2.8 Damar resin 3.5 Ethyl acetate n K159i) Xylene 73.0
This coating composition was used to coat toluene diisocyanate undercoated dbrous casing at room temperature using a doctor blade setup. A uniform coating of 0.10 to-0.14 thickness `was .obtained after a veminute heating atl9G C.'and an overnight air-dry. The
i6 undercoating Was obtained by passing the casing through an 0.25 percent solution of toluene diisocyanate in monochlorobenzene7 draining, air drying live minutes and heating live minutes at C. It was noted that undercoated casing could be boiled in tap water for three hours or stored in tap water at room temperature for three weeks with no sloughing of the coating. The rub and scratch resistance were still good and the Scotch tape removed an average of ten percent of the coating after immersion.
Example XXIX Sam-ples of fibrous casings were obtained and wet-out in Warm tap water. They were wiped between glass rods so that they had a surface moistness comparable to casing in process after passing the glycerol tank wiper rods.
Four hundred grams of toluene was made 0.25 percent in toluene diisocyanate and the .20-foot lengths of the casings were dipped through the solution. A small stainless steel tank with a Wooden bottom roller Was used. The casings were allowed -to stand at 25 C. .for ve minutes before placing them in an oven at to 105 C. The casings became hydrophobic with water contact angles (advancing) of 80 to 90.
The undercoated casings were coated with Saran resin and heated at 140 to 150 C. for six minutes. First attempts Vto coat were by dipping into an eight percent solution of Saran F-120 in methyl ethyl ketone. The room temperature was at 28 C. This elevated temperature caused blushing of the coating. VMethyl isobutyl ketone was added to the coating dope as a retarder. This eliminated the blushing.
The coated casings were allowed to stand over night. When tested for coating adhesion after a three-hour tap water boilby the Scotch tape test, the results were good as were also their rub Vand scratch resistance. No Sloughing in the tap water boil was noted.
Example XXX Eight in. Wide cellophane hlm was dipped through a solution of 0.5 percent 2,4-tolylene diisocyanate in carbon tetrachloride. The coated film was allowed to drain vertically for five minutes under ambient conditions and then heated at C. for five minutes. Pure water drops had a contact angle of about 80 on the surface and required about `one minute to wet through. The lrn was allowed to stand .one week under ambient conditions. The undercoated film was coated with a seven per cent solution of Saran resin in a suitable solvent .by dipping. After an air dry for ve minutes the polymer coating was baked for six minutes'at 13S-150 C. The coated cellophane was cut into two-inch strips to allow water to gain access to the interior and portions were placed in tap water for three hours at 9S9,8 C. No sloughing of the coating was noted. When the Vsurface was rapidly blotted dry after removal from the hot water and a oneinch clear Scotchtape afxed and rapidly pulled olf the coated film, an .average of 5% ofthe coating was removed in twenty trials. After a two-month storage of the coated film in tap or city water or deionized water at room tempcrature, no sloughing was noted and about Vlive per cent of the coating could be removed with Scotch tape.
Example XXXI Four diisocyanate and one triisocyanate weremade "by slowly adding a pure diamine or glycol or a solution thereof to a rapidly stirred 2,4 tolylene diisocyanate. The mole ratio was two of the diisocyanate to one ami-ne or glycol for making the diisocyanate and Ythree diisocyanate to one mole glycerol for making the triisocyanate. One ends up primarily with a urethane or urea that has essentlally free isocyanate groups on a larger molecule. A small amount of polymer also forms. Heat is evolved and. 1nduction periods were noted for the urethane formation. The isocyanates formed were then used to undercoat cellophane film at .high `enough temperatures and heated -for` long enough times so that essentially no free isocyan- 0.5 percent solution of meta-nitrophenyl isocyanate was made in carbon tetrachloride. Cellophane film was dipped through this solution, drained vertically and ten minutes later O-foot lengths were heated at 120 C. for three minutes. After the lm was allowed to stand over night, the initial advancing contact angle of water on the ilm was 80. Water wet through the surface lm in about one minute. A distinct water mark could be seen on the film surface if a water drop was placed on and removed 20 seconds later. The undercoated film was coated with 200centipoise saran resin lin methyl ethyl ketone by dipping to give a 0.20 mil coating. When the coating adhesion was tested with Scotch tape after a three-hour heating in city water at 95 C. no coating sloughing was noted and the average coating removal was 60 per cent.
Example XXXIII P-phenylene diamine and 2,4-tolylene diisocyanate were reacted in a 2:1 mole ratio. This new isocyanate still contains two isocyanate groups per molecule. A slightly warmed solution of 7.48 grams of the diamine in chloroform was added with rapid stirring to 24 grams of the diisocyanate. About 200 grams solvent was used. Heat was evolved and a major part of the product precipitated. The slurry was allowed to stand at room temperature for 24 hours. A portion of the uniform slurry was added to carbon tetrachloride to make a 0.2% solution of the solid. This solution was used to treat cellophane film as in Example XXX. 'I'he undercoated lm was held three days and coated land tested. Similar results were obtained.
Example XXXIV Pure, just molten hexamethylene glycol (29.5 grams) was added slowly with stirring to 87.5 grams of tolylene 2,4-diisocyanate. An induction period within which no heat was evolved was noted. The ask was then cooled to keep the temperature at about 60 C. A brownish liquid resulted which solidified slowly over the day. Benzene was added to make a 50% solution which was liquid at room temperature.
An 0.5% solution in benzene of this new diisocyanate was made and cellophane film dipped as before. The air dry iilm was very tacky, but the baked iilm was non-tacky at room temperature. When the undercoated lm was Saran-coated as in Example XXX, about 30% coating was removed in the adhesion tests. The adhesion of Parlon, Plioiilm, cellulose nitrate, and ethyl cellulose layers to the undercoated film was also promoted.
Example XXXV Similarly, 43.36 grams of pure ethylene glycol was added drop by drop to 235 grams of tolylene diisocyanate over a 70 minute period. No heat was evolved for l5 minutes, then the ask become so hot it could not be touched. A red-brown liquid resulted which solidified to an amber solid. While liquid, threads of material could be removed with a stirring rod. This indicated formation of small amounts of polymer from the slight excess of glycol used.
A 50% solution of the product in acetone was liquid at room temperature, but one week later had started to gel. acetone and to the fact that the acetone is a slightly enolizable compound.
An 0.5% solution was made by diluting the acetone solution with benzene. This was used to undercoat cellophane lrn as before. The air-dry undercoated film was not so tacky as was the lm undercoated with the hexamethylene glycol urethane. The baked film was nontacky. When coated and adhesion tested, similar results vwere obtained as in Example XXX.
This Was probably due to traces of water in the 18 Example XXXVI Similarly, 20.10 grams of pure (9S-100% ethylene diamine was slowly added to rapidly stirred 174.2 grams of tolylene diisocyanate. .Here no appreciable induction period was noted. Heat was evolved, and the product solodiiied when cold. A solution of 0.5% was made up in anhydrous ethyl acetate and a cellophane iilm was dipped through and treated completely as in Example XXX. Similar results were obtained.
Example XXXVII A urethane type of triisocyanate was made by slowly adding 9.3 grams of essentially anhydrous glycerol to 52.5 grams of Mondur TDS (a mixture of 2,4 and 2,6- tolylene diisocyanate with about of the 2,4 isomer present). After Aan induction period of about ten minutes, a large amount of heat was evolved, and the amber solu- Ation solidified as the temperature fell below 60 C. The
product was soluble in benzene. An 0.5 solution was made in benzene and cellophane film was treated analogously to Example XXX with about 5% of the coating being removed in the Scotch tape adhesion test.
The temperature at which the isocyanate undercoating may be carried out may be varied widely. Basic catalysts may be used as is well known in the art. Generally, with most cellulosic materials, any isocyanate present will be destroyed by the large excess of active hydrogen compounds present in the cellulose film.
From the foregoing description, it will be seen that all ,of the objects and advantages recited for my invention can be obtained in a convenient, simple and practical manner.
Having thus described my invention, I claim:
l. A coated substrate consisting essentially of a hydrophilic first layer of cellulose fibres impregnated with regenerated cellulose and having a thin layer of hydrophobic thermoplastic polymer bonded in direct contact to a surface of said first layer which has been reacted with an organic isocyanate to a superficial depth such as to be accompanied by an increase in film weight of 0.1 to 0.001%, said reacted surface of the hydrophilic layer being hydrophobic, said coated substrate being free of unreacted organic isocyanate and said polymer being free of reaction products thereof with organic isocyanate.
2. A coated substrate according to claim 1 wherein the hydrophobic polymer is a vinyl chloride-acrylonitrile copolymer.
3. A coated substrate according to claim 1 wherein the hydrophobic polymer is a vinyl chloride-vinylidene chloride copolymer.
4. A coated substrate according to claim l wherein the hydrophobic polymer is vinylidene chloride-acrylonitrile copolymer.
5. A coated substrate `according to claim l wherein the hydrophobic polymer is vinyl chloride-vinyl acetate copolymer.
6. A laminate consisting essentially of a hydrophilic cellulosic layer having a surface reacted with a compound containing at least one -X=C=Y group wherein X is selected from the group consisting of -C and N and Y is selected from a group consisting of O, S and NR Wherein R is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals, said reacted surface being hydrophobic, and a thin layer of hydrophobic organic material adhering directly to said reacted surface, said organic material being essentially free of reaction products thereof with organic isocyanate and said laminate being free of the unreacted compound.
7. A laminate according to claim 6 wherein the compound reacted with the surface of the hydrophilic cellulosic layer is toluene diisocyanate.
8. A laminate according to claim 6 wherein the compound reacted with the surface of the hydrophilic ce1- lulosic layer vis diisocyanatodiphenylmethane.
9. A laminate according to claim 6 wherein the com- A19 pound reacted with the surface of the hydrophilic cellulosic layer is stearyl isocyanate.
.10. A laminate consisting essentially of a hydrophilic cellulosic layer having a hydrophobic surface resulting 'R-is selected from the group consisting of hydrogenand monovalent hydrocarbon radicals, and a thin layer of rubber hydrochloride directlyadhering to said hydrophobic surface and free of reaction products thereof with said compound, said laminate being free of the uncombincd v compound.
vofthe unreacted compound and the reaction products of said compound with the Saran layer.
l2., A laminate consisting essentially of a hydrophilic cellulosic layer having a surface reacted with a compound containing at least one XFC-Y group wherein X is yselected. from theV group consisting of C and N and Y Yis selected from a group consisting of O, S and NR wherein R is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals, said reacted surface being' hydrophobic, .and a thin layer of Vinyon in direct, contact with and adhering to said reacted surface,
jsaid laminate being free of the unreacted compound and the reaction products of said compound with the Vinyon. 1 13. A laminate consisting essentially of a hydrophilic ,cellulosic layer having a surface reacted with a compound containing at least one X=C=Y group wherein X is selected from the group consisting of C and N and Y is selected from a group consisting of O, S and NR whereinvR is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals, said reacted surface-being hydrophobic, and a thin layer of polyethylene in direct, contact with and adhering to said reacted sur -face, said laminate being free of unreacted compound and .reaction products ofsaid compound with polyethylene.
14. A laminate consisting essentially of a hydrophilic cellulosic layer having a surface reacted with `a compound containing at least one X=C%Y group wherein'X is `selected from the group consisting of C and N and Y is selected fromagroup consisting of O, S andNR wherein R lis selected from thegroup consisting of hydrogen' and monovalent hydrocarbon radicals, said reacted sur- Yface being hydrophobic, and ay thin layer of chlorinated ,rubber in direct contact with and adhering to said reacted surface, said laminate being free of unreacted compound and reaction productsfof said compound with the chlorinated rubber layer. Y Y
l5. A laminate Vconsisting essentially of a. hydrophilic cellulosic layer having a surface reacted with a compound containing at least one X:C=Y group wherein X is lselected from the group consisting of C and N and Y Vis selected from a group consisting of O, S and NR Wherein R is selected from theV group consisting of hydrogen and monovalenthydrocarbon radicals, said reacted surface being hydrophobic, and a thin layer of hydrophobic .organic materialeselected from the group consisting of cellulose nitrate, cellulose acetate and ethyl cellulose in Adirect contact with and adhering to said reacted surface, rsaid laminate being free of unreacted compound and reaction products of saidcoinpound with theorganic ma- 20 16. 'A laminate consisting essentially of a hydrophilic cellulosic layer having 'a surface reacted with a compound containing at least one XrCbY group wherein X is selected from the group consisting of C and N and Y is selected from a group consisting of O, S and NR where- 4in R is selected from the group consisting of hydrogen land monovalent hydrocarbon radicals, said reacted surface being hydrophobic, and a thin hydrophobic layer of wax nitrocellulose in direct contact with and adhering to said reacted surface, said laminate being free of unrelacted compound and reaction products of said compound with the wax nitrocellulose layer.
17. In the process of coating a hydrophilic cellulosic base, the steps which consist of applying compound to a surface of a normally hydrophilic cellulosic base, which compound is of the cls containing XICZY wherein X is selected from the group consisting of Nrand C and Y is selected from the group consisting of O, S and NR wherein R is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals, maintaining conditions under which thecompound will react with the surface of said cellulosic base, continuing the reaction until substantially no unreacted compound remains so as to form a hydrophobic surface on said hydrophilic base to which a coating of hydrophobic polymer will directly bond, controlling the depth of modification of the surface of the cellulosic base so as to increase the weight Vof the base by only from 0.1 to 0.001% so that essentially only the surface of the base is modified from its normally hydrophilic character, and applying a coating of hydrophobic polymer to said reacted surface.
18. In the process of coating a hydrophilic cellulosic base, the steps which consist of modifying the surface characteristics of a normally hydrophilic cellulosic base by first bathing the surface of the cellulosic base with a dilute solution of organic isocyanate and solvent, then heating the treated base in ambient air and at a temperature to remove the solvent and to react the organic isocyanate with the cellulosic surface, the heating being continued until essentially all the organic isocyanate has been reacted therewith so as to form a hydrophobic surface on said hydrophilic base to which a coating of hydrophobic polymer will bond, controlling the depth of modification of the surface of the cellulosic base so as to increase its weight by only from 0.1 to 0.001% whereby essentially only the surface of the base is modified from its normalvly hydrophilic character, and applying a coating of hydrophobic polymer to said reacted surface.
19. In the process of bonding hydrophobic polymeric material toa hydrophilicV cellulosic base film, the steps which consist of treating a surface of the film while in a moist state with a solution of low water-soluble organic solvent containing from 10.0 to 0.005% weight of organic isocyanate, baking thel'm at a temperature and for a Vtime interval suflicient to completely react the organic isocyanatewith the surface material of the iilrn so as to im- ;part a hydrophobic character to the surface of thelrn, lthe depth to which the organic isocyanate penetrates the cellulosic -base being so restricted that .the reaction adds from 0.1 to 0.001% to the weight of the film whereby essentially only the surface of the hydrophilic base assumes ,hydrophobic characteristics, and when completely reacted subsequently coating the treated surface with a Vthin layer of the hydrophobic polymer.
20. In the process according to claim 19 wherein the concentration of organic isocyanatc in the solvent is in the vicinity of roughly one percent.
2l. A film consisting essentially of a hydrophilic cellulosic base having a surface reacted to a superficial depth with compound containing at least one XICY group wherein X is selected from the group consisting of C and VN and Y is selected from the group consisting of O, S and NR wherein R is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals, said reacted surfaceV being hydrophobic and essentially devoid of such unreacted compound, the reaction prod- 21 ucts of said compound adding between 0.1 and 0.001% to the weight of the film, said film other than its said reacted surface being hydrophilic.
22. A flexible tube consisting essentially of a regenerated cellulosic base having an organic isocyanate-reacted surface, said surface being hydrophobic and essentially devoid of free isocyanate, and said isocyanate reacted surface adding from about 0.1 to 0.001% to the weight of the nlm, and said film other than its reacted surface being hydrophilic.
23. A flexible sheet consisting essentially of a base of cellulose fibers impregnated with regenerated cellulose and having a hydrophobic organic isocyanate reacted surface, said sheet being essentially devoid of unreacted isocyanate, said isocyanate reacted surface adding from about 0.1 to 0.001% to the weight of the iilm, said ilm other than its said reacted surface being hydrophilic.
24. A flexible lamination having good strength, shape retention without stretching and resistance to moisture vapor and oxygen transmission consisting essentially of a film of hydrophilic cellulosic material having a superficially thin hydrophobic surface consisting of the in situ reaction products of organic isocyanate with said material,4
and to which hydrophobic surface a thickness of hydrophobic resin directly bonds by forces obtained other than through a chemical interaction therewith, said thickness of hydrophobic resin being free of reaction products of organic isocyanate therewith, said lamination being essentially devoid of free organic isocyanate and resistant to separation when contacted by hot and cold water.
25. A flexible lamination according to claim 24 wherein the reaction products include cellulose urethane and add by weight to from about 0.1 to 0.001% of the cellulosic film.
26. A lamination consisting essentially of a film of cellophane having a hydrophobic surface consisting of the reaction products thereof with a compound containing an -XI =Y group wherein Y is from the group consisting of -C and N and Y is from the lgroup consisting of O, S and NR wherein R is from the group consisting of hydrogen and monovalent hydrocarbon radicals, and a thickness of polyethylene directly contacting said reacted surface and strongly bonded thereto, said lamination being devoid of the compound in its free state, and the polyethylene being free of reaction products thereof with said compound.
27. A process of bonding polyethylene to cellophane which consist of the steps of treating at least one surface of the cellophane with a dilute solution of compound containing an :(#Y group wherein X is from the group consisting of -C and N and Y is from the group consisting of O, S and NR wherein R is from the group consisting of hydrogen and monovalent hydrocarbon radicals, heating the treated surface to react the compound with said surface of the cellophane, continuing the step of heating until no portion of the compound capable of reacting with the cellophane remains, the penetration of said solution being confined to the cellophane surface and so that the reaction products after baking adds from 0.1 to 0.001% to the weight of the cellophane whereby the cellophane retains its hydrophilic character other than at said surface, and then applying directly to said reacted surface a thickness of polyethylene.
28. A coated substrate consisting essentially of a first layer of active-hydrogen containing hydrophilic material having a hydrophobic surface contacted by a thin layer of hydrophobic polymer which is strongly bonded thereto, said hydrophobic surface comprising the reaction products of said hydrophilic material with organic isocyanate, and said layer of hydrophobic polymer being essentially free of organic isocyanate and reaction products of organic isocyanate with the material of said layer.
29. A coated substrate according to claim 28 wherein the hydrophobic polymer is of the class which do not contain active hydrogens in their molecular structure.
30. A coated substrate consisting essentially of a substrate of hydrophilic cellulosic material having a coating of hydrophobic polymer contacting one surface thereof and strongly adhering thereto, said one surface comprising the hydrophobic reaction products of organic isocyanate with the hydrophilic cellulosic material, said reaction products adding about 0.1 to 0.001% to the weight of the substrate, said substrate being otherwise hydrophilic, and said coating of hydrophobic polymer being essentially free of organic isocyanate and reaction products of organic isocyanate with the material of said coating.
31. A coated substrate consisting essentially of a substrate of hydrophilic cellulose fibres impregnated with regenerated cellulose and having a hydrophobic surface to which a thin layer of organic material of the class which do not contain active hydrogens in their molecular structure is directly and strongly bonded, said hydrophobic surface of the substrate consisting essentially of the reaction products of the said substrate surface with organic isocyanate including cellulose urethan; said reaction products adding about 0.1 to 0.001% to the weight of the substrate.
32. A coated substrate according to claim 31 wherein the hydrophobic surface also includes reaction products of organic isocyanate with compounds contained in the substrate selected from the group consisting of glycerol, water and mixtures thereof.
33. A coated substrate consisting essentially of a first layer of hydrophilic cellulosic material having a surface thereof reacted with organic isocyanate to a superficial depth which adds about 0.1 to 0.001% to the weight of the first layer, and a thin coating of a copolymer of vinyl chloride and vinylidene chloride contacting and adhering directly to said reacted surface, said coating being free of unreacted organic isocyanate yand reaction products of said organic isocyanate therewith.
34. A coated substrate consisting essentially of a first layer of hydrophilic cellulosic material having a surface thereof reacted with organic isocyanate to a superficial depth which adds about 0.1 to 0.001% to the weight of the first layer, and a thin coating of vinyl chloride-acrylonitrile copolymer directly contacting said reacted surface, and the coating itself being essentially free of unreacted organic isocyanate of reaction products thereof with organic isocyanate.
References Cited in the file of this patent UNITED STATES PATENTS 2,173,029 Waltman et al Sept. 12, 1939 2,284,895 Hanford et al .lune 2, 1942 2,370,405 Kaase et al. Feb. 27, 1945 2,415,839 Neal et al Feb. 18, 1947 2,430,479 Pratt et al Nov. 11, 1947 2,471,905 Smith May 3l, 1949 2,698,242 Saner Dec. 28, 1954 2,702,773 Penn et al Feb. 22, 1955 OTHER REFERENCES Sommers: Progress With New Polymers, British Rayon and Silk Journal, November 1953, pages 62 and 63.